I. Field of the Invention
This invention relates generally to automatic packaging machinery, and more specifically to the design of a film former used therein which may be used to create a wrapper for brochures, flyers and similar literature, the wrapper being specifically constructed so as to present a pleasing, uninterrupted pattern over the major surfaces of the wrapper.
II. Discussion of the Prior Art
A wide variety of packaging and bag making machines which utilize polyethylene or other suitable thermoplastic film materials are known in the art. However, until the present invention, none has been able to adequately and efficaciously handle paper products such as those encountered in the bulk mailing industry. In this application, stacks of individual sheets are deposited by a collator onto an infeed conveyor leading to the wrapping machine. The infeed conveyor includes suitable pushers for maintaining a predetermined spacing between individual stacks to be wrapped. Because of the nature of the product, it must be handled on a continuous rather than intermittent basis and, furthermore, it is required that the stack of literature or documents be supplied in a straight-line to the wrapping station. Where either intermittent stepping of the machine or directional changes are encountered, the inertia tends to cause the individual documents to be splayed out making the wrapping operation significantly more difficult.
It is also oftentimes desirable to provide decorative artwork or graphics on one or both side surfaces of the flat package. Thus, a seal line down the center of the package cannot be used if unsightly discontinuities in the graphics are to be avoided. Then too, when doing wrappings for bulk mailing, it is common that the wrapper have a small transparent "window" in the graphics through which addressing labels on the material packaged therein is visible. This dictates that the literature materials being wrapped be sufficiently constrained from moving within the package so as to have the addressing information no longer aligned with the window.
In the Shanklin et al U.S. Pat. No. 4,219,988 there is described a wrapping machine for wrapping packages in heat sealable thermoplastic film. The supply roll of film is prefolded longitudinally and at an inverting head the film is made to surround the product to be packaged prior to being moved through a side sealer where the loose edges are joined to form a tube. This type of sealing requires that the selvage at the sealed edge be trimmed off and disposed of. Finally, the tube with the packages therein appropriately is spaced and fed into an end sealer which serves to create a seal in a zone between adjacent packages while simultaneously severing the tube transversely to form individual sealed packages.
Machines like those described in the Shanklin et al U.S. Pat. No. 4,219,988 tend to have serious drawbacks. Specifically, the handling of the selvage has proven to be a significant problem in high speed packaging machines of the type described. The edge scrap cut loose tends to become electrostatically charged and is therefore difficult to handle. Attempts at winding the selvage onto a reel have not been altogether successful in that the machine must be periodically shut down for reel replacement, thus limiting the output production of the machine. Furthermore, when the edge seal is formed in such a fashion that the cutting loose of the selvage occurs simultaneously at the site of the seal, it is sometimes difficult to maintain the integrity of the seal. Thus, when the wrapped package of loose individual sheets is handled, there is a considerable likelihood that the seal will rupture and that the sheets comprising the contents may fall out the imperfectly sealed side edge.
The packaging machine of the present invention obviates all of the foregoing deficiencies of known prior art machines for wrapping sheet goods such as packs of printed literature and the like. These results are achieved principally by the incorporation of a unique film former which is disposed in the path of the film and in general, straight-line relationship to the infeed conveyor supplying the sheet goods to be packaged. The former which is utilized is operative to produce a generally flat rectangular tube around the stack of sheet goods fed into the former by the infeed conveyor. The tube is such that one major surface has a predetermined edge border turned inward and the remaining major surface of the rectangular tube overlaps that border. Upon exit from the film former, the tube containing the product is fed to a side sealer which is positioned to create a continuous longitudinal seal a predetermined distance inward from the extreme edge of the package in the zone where the second major surface overlaps the turned-in border portion of the first major surface. Following the side sealing step, the package is fed through an end sealer which creates a fusion bond transversely to the side seal and at locations which are spaced in accordance with the spacing maintained between individual packs of printed literature to be packaged arriving from the infeed conveyor. This end sealing operation also severs the package loose from the rest. Because of the manner in which the film material is turned inward at the edge or border of the first major surface, following end sealing, the package is sufficiently tacked together so that the sheets comprising the product cannot fall out of the package even if the side seal should be faulty.
In that the side seal line is not at the extreme edge of the package, it is less likely that such a side seal will rupture which is not the case in prior art arrangements. Then too, the film former of the present invention obviates the need for trimming the package following the side sealing step. Therefore, there is no selvage to deal with. Because no edge trimming is required the integrity of the graphics is maintained, adding to the aesthetic appearance of the resulting package.
Furthermore, by providing a degree of adjustability to the film former, the overall width of the flat tubular package can be accurately controlled so that any address information which may be printed on materials contained within the package can be made to line up with a transparent window zone.